1. Field of the Invention
The present invention relates to a transmission type screen adapted to be used for a projection type television receiver, and also relates to a method of manufacturing thereof. In particular, the present invention relates to a transmission type screen whose contrast is not lowered substantially even under external light illumination.
2. Description of the Related Art
As shown in FIG. 25A, a transmission type screen having such an arrangement that a lenticular lens sheet 48 is superposed on the front surface of a Fresnel lens sheet 26 having a Fresnel lens 45 has been conventionally used.
Further, the lenticular sheet 48 is made of a base material mixed therein with a light dispersing material such as glass or polymeric materials, and is formed at its both surfaces with cylindrical lenticular lenses 2, 5. Further, non-light converging parts of the light emission side lenticular lens 5 are formed respectively thereon with protrusive light absorbing layers 3 (which will be hereinbelow denoted as "black strips") at predetermined pitches in order to prevent the contrast of the transmission screen from being lowered by the external light.
However, in general, the above-mentioned conventional lenticular lens sheet 48 is mingled therein with the light dispersing material 4 such as glass beads or polymeric beads which are projected in part from the outer surfaces of the cylindrical lenses 5 and the black stripes 3 defined by the protrusive non-light converging parts, as shown in FIG. 25b, in order to focus an image and to enlarge the vertical viewing angle range.
Further, slight concavities and convexities are formed on the outer surface of a die for forming the surface of the lenticular lens sheet which is nearest to the viewer. These concavities and convexities are transferred to the outer surface of the lenticular lens sheet during molding so as to form an irregular reflection surface thereon in order to prevent objects surrounding the screen from being reflected therein.
Accordingly, when the external light is irradiated onto the light emission side surface of the lenticular lens sheet 48, irregular reflection occurs causing the screen surface to be whitish and the contrast to be deteriorated. Further, in order to improve the contrast of the screen even under irradiation of the external light, a mirror surface plate made of glass or transparent plastic which lowers the light transmissivity is attached to the front surface of the screen. However, this further causes external light (from fluorescent lamps, incandescent lamps, surrounding persons, windows or the like) to be highly reflected in the screen, and accordingly, the visibility of an image thereon becomes lower.